The proposed research is aimed at understanding social interaction and olfactory communication in a mammalian species. The Mongolian gerbil (Meriones unguiculatus) is the model for this investigation. At this time we know a great deal about the hormonal and environmental control of scent marking behavior and have established a new signaling system involving the Harderian gland located behind the eye ball in most vertebrate species. Our current and future work is focusing on the interaction among signaling systems and their modification by metabolic parameters. Future work is intended to detail the relationship between reproductive fitness, olfactory communication and ultrasonic emissions. Metabolic parameters will be altered by manipulation of the diet, and thermoenergetic processes manipulated by altering body temperature and social interactions. Ultrasonic communication depends in part on pheromone emission and the latter appears to be diet specific. It is this relationship which will be studied during the next year. Hopefully we will be able to see how animals interchange signals during social interactions and the degree to which they are dependent on thermoenergetic factors. Ultimately we wish to point out the reproductive significance of these parameters. BIBLIOGRAPHIC REFERENCES: Thiessen, D.D., Clancy, A. & Goodwin, M. Harderian pheromone in the Mongolian gerbil (Meriones unguiculatus). J. Chem. Ecol., in press, 1976. Thiessen, D.D., Graham, M., Perkins, J. & Marcks, S. Temperature regulation of social grooming in the Mongolian gerbil (Meriones unguiculatus). Behav. Biol., in press, 1976.